ANTIBIOTICS

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ANTIBIOTICS
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The Selection of Antibiotic
The selection of antibiotic therapy for an
infection requires a knowledge of 1The
infecting organism, including the pathogen most
likely to be present in given clinical or
geographical circumstances 2The local patterns
of antimicrobial resistance in common pathogens
3 An understanding of the pharmacokinetics of the
antimicrobials selected 4 The physiology of the
patient, metabolic upset, renal or hepatic
dysfunction, age and available routes of
administration. The clinical history should
determine the systems of the body most likely to
be involved in disease. Figure 6.3 (p. 133) shows
common pathogens found in different systems.
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ENDOGENOUS INFECTIONS-RESERVOIRS OF INFECTIONS IN
ADULTS
The human body is in contact with many
potentially infectious agents bacteria, viruses,
fungi or protozoa. Most are harmless colonisers
causing no clinical upset but forming a natural
reservoir of potential infection in the human host
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Common Infecting Organisms.
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Selection of Antibiotics

• Identification of Infecting organism

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Empirical treatment Prior to Identification of
Organism

• 1.The Acutely Ill patient
• 2. Selecting a Drug

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C.Determining the Antimicrobial Susceptibility of
the Organism

• Bacteriostatic vs Bacteriocidal
• MIC
• MBC
• D. Effect of Site of Infection on Therapy Blood
  Brain Barrier
• Lipid solubility of drug
• Mol wt
• Protein Binding

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E. Patient Factors

• Immune system
• Renal dysfunction
• Hepatic dysfunction
• Poor perfusion
• Age
• Pregnancy
• Lactation
• F. Drug Safety
• G. Cost of therapy

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• Route of Administration
• Determination of Rational Dosing
• 1 Concentration dependent killing
• 2. Post antibiotic effect

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SITES OF MICROBIAL ACTION
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Chemotherapeutic Spectra

• Narrow
• Extended
• Broad
• Combination of Antimicrobials
• Advantages
• Disadvantages

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DRUG RESISTENCE

• 1.Genetic alteration
• Spontaneous mutation
• DNA transfer of drug resistence
• 2. Altered expression of proteins in drug
  resistant organisms
• Modification of target sites
• Decreased accumulation
• Enzyme inactivation

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PROPHYLACTIC ANTIBIOTICS

• Rheumatic heart disease
• Dental work in pts with valves, prosthesis
• TB
• Surgery
• Pregnant mother - zidovudine

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COMPLICATIONS OPF ANTIBIOTIC THERAPY

• Hypersensitivity
• Direct toxicity
• Superinfections

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Inhibitors of Cell Wall Synthesis
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PENICILLIN
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PENICILLIN G
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Extended Penicillins

• ORAL
• - Amoxycillin
• IV
• -Ampicillin
• Wider range
• Broken down by penicillinase
• Combined with penicillinanse (BETA LACTAMASE)
  inhibitors -
• Clavulanic acid
• Sulbactam
• Tazobactam
• Augmentin- Amoxysulbactam

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Anti Staphylococcal Penicillins

• Oral Not inactivated by penicillinases (BETA
  LACTAMASE)?
• Cloxacillin
• Dicloxacillin
• Flucloxacillin

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ADVERSE EFFECTS OF PENICILLINS
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Stability of penicillins to acid
penicillinases
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CEPHALOSPORINS
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OTHER BETA LACTAM ANTIBIOTICS-CARBAPENEMS
MONOBACTAMS
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OTHER CELL WALL INHIBITORS- VANCOMYCIN

• SIDE-EFFECTS